Abrasive apron



March 23 1926. 1,577,485

J, M. NASH ABRASIVE APRON Filed June 19, 1925 Uv'- vmv... w

Fig 5 l e ATTORNEYS,

Patented Mar. 23, 1926.

UNITED STATES JOHN M. NASH, QF MILWAUKEE, WISCONSIN.

ABRASIVE APRON.

Application filed .Tune 19, 1925. Serial No. 38,283.

To all whom t may concern:

Be it known that I, JOHN M. NASH, a citizen of the United States, residing at Milwaukee, county of Milwaukee, and State of Wisconsin, have invented new and useful Improvements in Abrasive Aprons, of which the following is a specification.

My invention relates to improvements in abrasive aprons of the general type used in finishing and polishing machines, in which an apron such as sand paper is progressively fed from a roll and the worn end portions torn or cut away.

The objects of my invention are to increase the efiiciency of the aprons in operation upon work having abrupt changes in contour such as are produced by ribbingand channeling the work in a turning lathe; also to provide a form of apron in which waste will be reduced to a minimum.

Heretofore aprons of the above mentioned type have been partially subdivided into narrow strips by a series'of slits designedv to allow each such strip to operate to a certain extent independently in tilting or conforming to the contours of the work. These narrow strips were connected by a backing strip as set forth in my former patent numbered 725,761, dated April 21, 1903, and the machines in which such aprons are used are equipped with means for relatively shifting or vibrating the work (or the apron) in a direction parallel to the axis of the work at suitable intervals and in an attempt to bring the abrading strips into contact with all portions of work in the various stages of the operation.

In cases where revolving sheets have been actuated with. a whipping action upon relatively stationary surfaces of moldings and other materials having generally fiat surfaces, and also in cases where sanding belts have been employed, fairly good results have been obtained by slitting portions of such sheets or belts and leaving other portions unslitted. But such sheets and belts as heretofore constructed are not adapted to my purposes for the reason that the slitted strips are either so held that they are not permitted to freely conform to sharply defined circular contours, or are held by wide unslitted zones that must be cut away and wasted, for if used they destroy th abrupt contour lines.

Such aprons, as heretofore constructed,

have been open to two serious objections due to the fact that the slitting operation dislodged much of the abrasive material atv the margins of the strips and rendered such margins largely ineffective; also to the fact that the material in the transversely extending unslitted Zones could not conformy to sharp contour edges or depressions in such a manner as to reach all portions of the surfaces to be abraded without cutting away or rounding portions of such surfaces at points where sharply defined contours are desired.

More particularly stated, therefore, it is the object of the present invention to eliminate the above mentioned objections and provide an abrading apron, all portions of which are conformable to the surfaces to be abraded without destroying or cutting away the edges or angles of sharply defined contour variations such as sharp edged flanges or the walls of deep channels.

In the drawings:

Figure 1 is a diagrammatic View, in side elevation, showing the manner in which my abrasive apron is progressively fed to7 and held against the work.

Figure 2 is a front elevation of a fragment of my improved apron.

Figures 3 and 4L are sectional views drawn, respectively, to lines 3 3 and 4-4 of Figure 2.

Figure 5 is a fragmentary view on an enlarged scale, drawn generally online 5-5 of Figure 1.

Figures 6, 7 and 8 are detail views on a still larger scale showing the manner in which successive portions of my improved apron will conform to the sharp contour breaks in the left hand portion of the work shown in Figure 5.

Figure 9 is a fragmentary front elevation showing the position of portions of the several strips shown in Figure 8 when applied to the same portion of the work.

Like parts are identified by the same reference characters throughout the several views. y

My improved apron is initially wound in a roll 1 from which yit is fed over a guard 2 downwardly to the work 3 against which itis held by an elongated transversely disposed brush 4. The apro-n passes between a bar 5 and an eccentric guide 6 which may be adjusted to hold the paper against or substantially against the opposing surface of the bar 5. With the exception of the apron, all of the parts and features shownin Figure 1 are parts of polishing machines in common use and it may be assumed that either the bar 5 and associated guide 6 or the work itself may be adjusted along lines substantially parallel to the aXis of the work at intervals during the abrading operation. It may also be assumed that the work is supported and rotated about its own axis in contact with the abrading surfaces of the apron, the latter being advanced from time to time and the worn end portions torn or cut off manually, as in a machine of the general type herein referred to as disclosed in my prior Patent No. 763,315, dated June 21, 1904-.

It will be observed in Figure 2 that the abrasive apron is sub-divided by a series of slits 10 Ainto successive series of narrow strips 11 connected end to end with those of the next series of strips 11 by an unslitted transversely extending Zone 12. The working surface of the apron is provided throughout its length by an abrasive coating 13. The entire apron may be assumed to be formed from an elongated sheet of sand paper or other abrading material.

Referring to Figure 4 it will be observed that the apron is slitted by cutting into its rear surface to a sufficient depth to nearly or completely sever the material composing one of the strips 11 from that composing the adjacent strips. A cutting roller 15 having an annular knife edge 16 may be ernployed as illustrated in Figure i although it will be understood that the means for slitting the paper or backing material composing the apron is not essential and forms no part of the invention herein claimed. It is important, however, and essential to one portion of my invention, that the cutting be done from the rear side of the apron and in a manner to avoid dislodging the abrasive particles from the working surface, instead of cutting into the material from the front or abrading side as has heretofore been the practice.

The cutting or slitting operation is suspended by a relative separation of the cutting roller andV the apron within the area of the connecting zone 12, but instead of leaving a wide unslitted Zone, I bring the slits of the successive slitted zones into such proximity that any pressure applied to the apron within the Zone 12 or in its vicinity which tends to flex the apron will cause the material in the zone 12 to bend or flex along substantially straight lines following the lines of the slits. And there will also be a. tendency for thev slits to extend into the Zone 12 along these lines by tearing the material of which the apron is composed. Therefore, the material in the zone 12 will be caused to bend at a sharp angle as illustrated in Figure 6.

When the slitted portions of the apron are being applied to the same portions of the work as illustrated in Figures 7 and 8 the strips which register with outwardly projecting portions. of the work will tend to separate and lie obliquely on such surfaces` of the work. In the vicinity of zone 12 this separation will be slight as indicated in Figure 7, Whereas the portions of the apron substantially midway between the zones 12 are separated to a considerably greater extent as illustrated in Figure 8 and may overlap to some extent in the channels or annular depressions of the work as indicated in Figure 8. But owing' to the vfact that the separated strips tend to f2 lie obliquely upon the surfaces of the work with which they contact and also owing to the lateral vibration or periodic relative lateral adjustment of the work or of the apron above referred to, all surfaces of the work will be reached by the apron.

lt will also be observed in Figures 6, 7 and 8 that a portion of the apron will in any event lie flat at the base of a channel in the work as indicated at 19. If a slitted portion of the apron is so operating, the strip, will ordinarily be narrow enough to be received in the channel as clearly shown in Figure 8, whereas if the unslitted zone 12 is. in operation upon this portion of the work flexion will take place along the lines corresponding with the slits and in a manner to allow a portion of the zone 1.2, having the same width as one of the strips, to rest at the bottom of the groove or channel. And at the same time the unslitted zone 12 will control the spreading of' the slitted portion of the apron on other portions of the work.

If the channel is of less width than the width of the strips the latter will tend to stand on edge but, inasmuch as the abrasive surfaces of the strips extend entirely to the edge thereof they cut or abrade the work in almost exact conformity to the designed contour and the bottom of the channel will also be abradedand finished for the reason that the beveled marginal portions 2O of the strips are more flexible than the central portions and will bendv sufficiently to run a part of the time upon the base of the channel. llhis action is facilitated bythe relative shifting of the worlr and the apron as above described.

In the use of my improved apron it will be manually advanced from time to time as the abrading surface becomes worn and whenever an unslitted zone passes the work by reason of such advancement the Worn slitted portion bel-ow or beyond it may be cut away and removed. It is not necessary at any time to cut the apron above the work or to remove the unslitted portion before it reaches a point where it will operate upon the work. Therefore, the entire area of the slitted and unslitted zones may be utilized instead of wasting from one-quarter to oneifth of the apron in accordance with the practice heretofore prevailing of using the slitted portions of the aprons only and drawing the unslitted portions across the work without action thereon.

It will be understood that while no exact dimensions in the' width of the unslitted zones is essential, yet it is essential to the accomplishment of that portion of my object which relates to the prevention of waste that the unslitted zone shall be sufficiently narrow to allow iexion to take place freely as above described. I have found that by making the unslitted zones substantially one-eighth of an inch wide very satisfactory results can be obtained, whereas if these zones exceed one-quarter of an inch in width, satisfactory results in the use of these portions of the apron for abradng sharply defined contours will not be obtained.

Great importance is also attached to the form of the slitted portions of the apron whereby each of the narrow strips has a cross section which is substantially an isosceles trapezoid, the longer dimension of which carries the abrasive.

I claim:

1. An abrasive apron for polishing machines slitted longitudinally to provide zones of longitudinally extending narrow strips substantially in lateral contact, each independently conformable to the surface contours of the work and each having the abrasive material extended wholly to the side margins of the strips and substantially contiguous to the side margins of adjacent strips, whereby the abrasive material in such apron will be substantially continuous across all of said strips throughout the width of the apron.

2. An abrasive apron for polishing machines slitted longitudinally to provide zones of longitudinally extending narrow strips, each independently conformable to the surface contours of the work and each having margins inclined from their rear surfaces laterally toward the margins of their abrasive surfaces to form relatively flexible abrasive margins having a wedge shaped cross section.

3. An abrasive apron for polishing machines partially slitted to provide series of narrow longitudinally extending strips, each of said strips having beveled side margins and its widest face coated with abrasive material extending to the extreme edges of said side margins.

JOHN M. NASH. 

